A conventional station-building power-supply device absorbs regenerative energy caused by an electric vehicle and generated on a high-voltage DC side of an overhead line, converts DC power into AC power, and supplies the AC power to station-building facilities on a low-voltage AC side of a station-building AC system. A voltage value of the overhead line rises when the regenerative energy is generated, for example, at the time of deceleration of the electric vehicle. The station-building power-supply device compares the overhead line voltage value with a regeneration determining voltage value for determining whether the electric vehicle connected to the overhead line performs regenerative operation and, when the overhead line voltage value is higher than the regeneration determining voltage value, performs power-absorbing operation. Such a technique is disclosed in Patent Literature 1 below.
In order to efficiently absorb the regenerative energy in the station-building power-supply device, the regeneration determining voltage value is desirably set to be slightly higher than a no-load voltage value that is a voltage value of the overhead line in a no-load state where no voltage change due to power running and regeneration Occurs.